Longitudinal Acoustic Wave Velocity Research Articles

Study of the Acoustic Characteristics of Suspensions Based on Glycerol and Synthetic Diamond Microparticles Using a Resonator with a Longitudinal Electric Field

The acoustic properties of suspensions based on pure glycerol and diamond powder with a particle size of 1–2 μm and different concentrations were studied using a resonator with a longitudinal electric field. A disk resonator made of langasite with round electrodes on both sides of the plate with a frequency of 4.1MHz, operating on a longitudinal acoustic wave, was completely immersed in a liquid container with the studied suspension. Based on the measured frequency dependences of the real and imaginary parts of theelectric impedance of the resonator using an equivalent electromechanical circuit, the longitudinal elastic modulus and longitudinal viscosity coefficient of the samples were determined. Comparison of the experimental dependences of the longitudinal elastic modulus, viscosity coefficient, and longitudinal acoustic wavevelocity on the volume concentration of diamond particles in the suspension with the calculated dependences demonstrated good agreement.

QUANTITATIVE ANALYSIS OF THE DISTRIBUTION OF LOCAL POROSITY IN CARBON FIBER STRUCTURES BY LASER OPTOACOUSTIC METHOD

Currently, an urgent problem is the development of non-destructive diagnostic techniques for quantifying the level of local porosity of composite structures. The paper presents a method for estimating the porosity of a material from the experimentally measured phase velocity of longitudinal acoustic waves propagating in it. Laser excitation of ultrasound was used to create probing pulses. Porosity was calculated using experimentally measured phase velocities of longitudinal acoustic waves propagating in the composite. The proposed method allows one-way access to the object during measurements, which makes it possible to study structures of variable thickness and complex shape. The possibility of obtaining distributions of local porosity values in the studied section of the structure is demonstrated by the example of three carbon fiber stringer panels. The study showed that locality of the porosity value and its change from point to point plays an important role in such constructions, and the maximum local porosity of this area of the panel may differ from the average volumetric porosity by more than two times. The possibility of obtaining a “map” of the distribution of the local porosity of the panel section in the plane of laying the carbon fabric is also demonstrated. This method is quite operational, which allows it to be used within the framework of real production in order to improve the conditions and methods of production.

Лазерно-ультразвуковое исследование распределения локальной пористости в углепластиковых стрингерных панелях

The paper presents a method for quantifying the porosity of carbon fiber structures based on laser excitation of probing ultrasonic pulses. A method for estimating the porosity of a material from the experimentally measured phase velocity of longitudinal acoustic waves propagating in it is proposed. Using the example of control samples and real structures made of carbon fiber, the possibility of obtaining distributions of local porosity values in the studied section of the structure is demonstrated. It is shown that in the studied structures there are regions with a significant variation in the value of local porosity. The proposed method can be used to control the quality of manufactured composite structures, as well as to study the internal changes in structure during operation.

Electronic, Optical, and Elastic Properties of CaFI Monolayer and Acoustic Phonon Dispersion at Hypersonic Frequencies Using Density Functional Theory and beyond with Random Phase Approximation and Bethe-Salpeter Equation.

The extraordinary properties of graphene have motivated us to investigate a novel 2D compound. In this framework, we study the structural, vibrational, electronic, optical, and elastic properties of a new two-dimensional CaFI monolayer, using DFT, GW, RPA, and BSE methodologies. The phonon dispersion curve of the CaFI monolayer exhibited no unstable phonon modes, confirming that this 2D sheet is dynamically stable. Our GW calculations show that the indirect bandgap energy value of CaFI is 6.52 eV. Interestingly, the bandgap rapidly decreased by improving the electric field value. Our BSE computations indicate that this monolayer becomes translucent when the incident light frequency exceeds the plasma frequency (6.50 eV). Also, we have computed the second and third elastic constants of CaFI by combining the DFT and RPA approaches with the homogeneous deformation method. Additionally, the longitudinal acoustic phonon dispersion of CaFI was studied. We have determined that the longitudinal acoustic wave velocity in our sheet is higher than the LA wave velocity of germanium measured using Brillouin or ultrasonic techniques.

Acoustic and acousto-optic properties of Ge-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- and Si-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- glasses in case diffraction on longitudinal and shear acoustic waves

We investigated acoustic and acousto-optic properties of glasses based on germanium, selenium, silicon and tellurium. The results of measurement are presented for two group of glasses including germanium, selenium and tellurium (GeSeTe) and silicon and tellurium (SiTe). The major characteristics of glasses such as the velocity of longitudinal and shear acoustic waves as well as the values of figure of merit are presented. The values of figure of merit are obtained by diffraction on longitudinal and shear acoustic waves at the wavelength of optical radiation λ = 3.39 μm. We also present the results of measurements of acoustic attenuation values α for longitudinal and shear acoustic waves in tellurium glasses at ultrasound frequencies in the range f = 75-100 MHz. Keywords: acousto-optics, acousto-optic figure of merit, germanium, selenium, silicon, tellurium, attenuation acoustic waves.

Ab initio исследования влияния давления на структуру, электронные и упругие свойства карбонатов щелочных--щелочно-земельных металлов

Density functional theory with a gradient PBE functional and dispersion correction D3(BJ) in the basis of localized orbitals of the CRYSTAL17 package was used to study the effect of pressure on the structural, electronic, and elastic properties of K2Ca(CO3)2, K2Mg(CO3)2, Na2Ca2(CO3)3, Na2Mg(CO3)2. The parameters of the third-order Birch-Murnaghan equation of state are determined, and it is shown that the equilibrium volume and compressibility modulus depend linearly on the average cation radius. Under pressure, the widths of the upper valence bands increase maximally in K2Ca(CO3)2 and minimally in Na2Ca2(CO3)3, while the centers of gravity of the cationic states shift by ~0.2 eV. Elastic constants and polycrystalline moduli are calculated, which increase with decreasing average cation radius. The shear modulus for K2Ca(CO3)2 and K2Mg(CO3)2 decreases with increasing pressure, and this leads to anomalous behavior of the longitudinal and transverse acoustic wave velocities.

Ab initio studies of the effect of pressure on the structure, electronic and elastic properties of carbonates of alkali-alkaline earth metals

Density functional theory with a gradient PBE functional and dispersion correction D3(BJ) in the basis of localized orbitals of the CRYSTAL17 package was used to study the effect of pressure on the structural, electronic, and elastic properties of K2Ca(CO3)2, K2Mg(CO3)2, Na2Ca2(CO3)3, Na2Mg(CO3)2. The parameters of the third-order Birch--Murnaghan equation of state are determined, and it is shown that the equilibrium volume and compressibility modulus depend linearly on the average cation radius. Under pressure, the widths of the upper valence bands increase maximally in K2Ca(CO3)2 and minimally in Na2Ca2(CO3)3, while the centers of gravity of the cationic states shift by ~0.2 eV. Elastic constants and polycrystalline moduli are calculated, which increase with decreasing average cation radius. The shear modulus for K2Ca(CO3)2 and K2Mg(CO3)2 decreases with increasing pressure, and this leads to anomalous behavior of the longitudinal and transverse acoustic wave velocities. Keywords: ab initio calculations, buchliite, eithelite, shortite, equation of state, elastic moduli, density of states, pressure.

Using Broadband Acoustic Spectroscopy with a Laser Source of Ultrasound to Study the Frequency Dependences of the Phase Velocity of Longitudinal Acoustic Waves in Porous Carbon Fiber Reinforced Plastic Composites

Using Broadband Acoustic Spectroscopy with a Laser Source of Ultrasound to Study the Frequency Dependences of the Phase Velocity of Longitudinal Acoustic Waves in Porous Carbon Fiber Reinforced Plastic Composites

Применение широкополосной лазерно-ультразвуковой спектроскопии для неразрушающего контроля пористости углепластиков с различным объемным содержанием углеродного волокна

In this work, to obtain the frequency dependences of the phase velocity of longitudinal acoustic waves in composite materials, we use the method of broadband laser-ultrasonic spectroscopy, based on laser thermo-optical excitation of broadband acoustic pulses. Unidirectional carbon fiber reinforced plasticsampes with different volume contents of the matrix and fiber were taken as objects of study.For the studied samples, the frequency dependences of the phase velocity were obtained in the spectral range of 0.8 – 10 MHz, and the existence of the phase velocity dispersion in this range was shown. The phase velocity dispersion of longitudinal acoustic waves in the sample was calculated using the phase spectra of the probe ultrasonic pulse and the pulse transmitted through the sample under study. It is also shown that the relative dispersion of the phase velocity characterizes the porosity of the sample, and the higher the porosity, the greater the relative dispersion. Empirical relations obtained for the relationship between porosity and relative dispersion can be used for the operational non-destructive assessment of the porosity of composites. The results obtained can be useful both for quality control of the materials obtained with the aim of modernizing manufacturing technologies and for predicting the behavior of structures and parts of this material under external loads.

Акустические и акустооптические свойства стекол Ge-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- и Si-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- в случае дифракции на продольных и сдвиговых акустических волнах

We investigated acoustic and acousto-optic properties of glasses based on germanium, selenium, silicon and tellurium. The results of measurement are presented for two group of glasses including germanium, selenium and tellurium (GeSeTe) and silicon and tellurium (SiTe). The major characteristics of glasses such as the velocity of longitudinal and shear acoustic waves as well as the values of figure of merit are presented. The values of figure of merit are obtained by diffraction on longitudinal and shear acoustic waves at the wavelength of optical radiation λ = 3.39 µm. We also present the results of measurements of acoustic attenuation values α for longitudinal and shear acoustic waves in tellurium glasses at ultrasound frequencies in the range f = 75-100 MHz.

Large Piezoelectric Response and Ferroelectricity in Li and V/Nb/Ta Co-Doped w-AlN.

Enhancement of piezoelectricity in w-AlN is desired for many devices including resonators for next-generation wireless communication systems, sensors, and vibrational energy harvesters. Based on density functional theory, we show that Li and X (X = V, Nb, and Ta) co-doping in 1Li:1X ratio transforms brittle w-AlN crystal to ductile, along with broadening the compositional freedom for significantly enhanced piezoelectric response, promising them to be good alternatives to expensive Sc. Interestingly, these co-doped w-AlN also show quite large spontaneous electric polarization (e.g., about 1 C/m2 for Li0.125X0.125Al0.75N) with the possibility of ferroelectric polarization switching, opening new possibilities in wurtzite nitrides. An increase in piezoelectric stress constant (e33) with a decrease in elastic constant (C33) results in an enhancement of piezoelectric strain constant (d33), which is desired for improving the performance of bulk acoustic wave (BAW) resonators for high-frequency radio frequency (RF) signals. Also, these co-doped w-AlN are potential lead-free piezoelectric materials for energy harvesting and sensors as they improve the longitudinal electromechanical coupling constant (K332), transverse piezoelectric strain constant (d31), and figure of merit (FOM) for power generation. However, the enhancement in K332 is not as pronounced as that in d33 because co-doping increases dielectric constant. The longitudinal acoustic wave velocity (7.09 km/s) of Li0.1875Ta0.1875Al0.625N is quite comparable to that of commercially used piezoelectric LiNbO3 or LiTaO3 in special cuts (about 5-7 km/s) despite the fact that the acoustic wave velocities, important parameters for designing resonators or sensors, decrease with co-doping or Sc concentration.

Theoretical and Experimental Study of the Effects of Impact Drilling Parameters on the Properties of Surrounding Rock Damage

Using a self-designed hydraulic impact drilling test-bed and rock core drill, six groups of cylindrical granite specimens (93 mm dia. × 200 mm) containing central axial holes formed either by impact or nonimpact drilling methods were tested in uniaxial compression to failure on an Instron 1346 universal testing machine to investigate their mechanics and damage properties. The longitudinal acoustic wave velocities were measured before testing. The rock specimens were grouped according to the method of drilling the central hole (impact load exerted by different impact power and different frequencies for an approximately identical impact power, or nonimpact drilling). In this study, a statistical constitutive damage model based on Weibull distribution was used to calculate the degree of rock damage after drilling center holes. The experimental curves were measured to analyze the damage evolution process and the radius of rock damage. These indicate that rock damage increased with the increase of impact power and decreased with increasing impact frequency at constant impact power. This was also verified by the measured longitudinal wave velocity in all rock specimens. These results have significance for guiding the design of composite rock drilling tools that are dedicated to improving rock-breaking efficiency.

Laser-ultrasonic nondestructive evaluation of porosity in particulate reinforced metal-matrix composites

In this work, we propose the laser-ultrasonic method for nondestructive evaluation of porosity in particulate reinforced metal-matrix composites fabricated by stir and in-situ reactive casting techniques. The method is based on the influence of porosity on dispersion of the phase velocity of longitudinal acoustic waves, which is measured by the broadband acoustic spectroscopy with laser excitation of ultrasound (laser-ultrasonic spectroscopy). We studied stir cast hypereutectic aluminum-silicon alloy A336 matrix composites reinforced with the SiC micro particles (3.3–13.5 vol%) and in-situ reactive cast Al/Al3Ti composites reinforced with the Al3Ti intermetallic particles (4–11.5 vol%). In the spectral range of 3–40 MHz, the phase-velocity dispersion in both types of composites was observed: the high-frequency velocity in the range of 20–40 MHz increases with the increase of the reinforcement content independent of porosity, whereas the low-frequency velocity in the range of 3–10 MHz decreases with the increase of porosity independent of the reinforcement content. As a result, the relative dispersion grows up with the increase in the composite porosity independent of the variation in the reinforcement content. The empirical dependence between the porosity in a scanning composite region and the relative phase-velocity dispersion in this region is approximated by the same unified function. For the first time, such unified porosity-phase velocity functional relationship is obtained for particulate reinforced metal-matrix composites completely different in fabrication techniques as well as in chemical composition and elastic properties of reinforcing particles.

Verification of the Kramers-Kronig relations between ultrasonic attenuation and phase velocity in a finite spectral range for CFRP composites

The aim of this work is to verify applicability of the Kramers-Kronig relations between the attenuation coefficient and phase velocity of longitudinal acoustic waves in carbon fiber reinforced plastic (CFRP) composites in a finite megahertz frequency range. To measure these characteristics, the method of broadband acoustic spectroscopy with a laser source of ultrasound is used. We have experimentally shown that absolute attenuation in CFRPs is determined by both absorption in a polymer matrix and scattering on carbon fibers and gas pores of several tenths of microns in size. We have also found that the increasing composite porosity leads to the decrease in the absolute value of the ultrasonic velocity and to the increase in its relative dispersion in the entire studied frequency range of 1–10 MHz. The experimental results have shown that for the studied CFRPs in this range, features of the mechanism causing attenuation and dispersion of longitudinal acoustic waves by propagation in composites do not influence on applicability of the local Kramers-Kronig relations.

Local Kramers–Kronig Relations between the Attenuation Coefficient and Phase Velocity of Longitudinal Ultrasonic Waves in Polymer Composites

The relationship between the experimentally obtained attenuation coefficient and dispersion of the phase velocity of longitudinal ultrasonic waves in polymer composite materials has been analyzed. The laser optoacoustic method has been used to measure the ultrasonic attenuation and velocity in a wide frequency range. Verification of the Kramers–Kronig relations for ultrasound-scattering and absorbing carbon fiber reinforced plastic (CFRP) composites has been performed using the analysis of the relationship between the frequency dependences of the attenuation coefficient and phase velocity of longitudinal acoustic waves in samples. We have shown that the Kramers–Kronig relations between the ultrasonic attenuation and phase velocity are valid within the 1–10 MHz frequency range without regard to a particular mechanism of the decay in the energy of an initial acoustic wave during its propagation in a composite.

In- and out-of-plane longitudinal acoustic-wave velocities and elastic moduli in h-BN from Brillouin scattering measurements

The elastic constants of high-quality, single-crystal hexagonal boron nitride (h-BN) have been measured by means of high resolution Brillouin spectroscopy using a modified reflected light microscope. The sound propagation velocity in the c-axis direction and perpendicular to the c-axis have been obtained from the Brillouin frequency shift, with a proper account taken of the vast difference between the ordinary and extraordinary refractive indices recently reported in the highly anisotropic layered h-BN crystal. The elastic constants c11 and c33 obtained from the Brillouin experiments are somewhat lower than previous determinations based on inelastic x-ray measurements and confirm the overestimation of the h-BN elastic constants by ab initio calculations based on density functional perturbation theory in the local density approximation.

Study of Porosity of Carbon Reinforced Plastic Composites Using Broadband Ultrasound Structuroscopy Techniques

Theoretical assessments are given for the use of the through-transition technique of broadband ultrasonic spectroscopy to determine porosity of heterogeneous materials. Experimental measurements of local porosity of composites using the through-transition technique are presented. Dependences of elastic moduli on the concentration of hardening particles and porosity of metal matrix isotropic composite found. Experimental relationship between the phase velocity of longitudinal acoustic waves and the power of structural noise in samples of graphite epoxy composites is obtained.

Influence of the porosity on the dispersion of the phase velocity of longitudinal acoustic waves in isotropic metal-matrix composites

The influence of the volumetric porosity of isotropic metal-matrix composite materials, which are reinforced with ceramic microparticles, on the dispersion of the phase velocity of longitudinal acoustic waves is investigated. For this purpose, the method of broadband acoustic spectroscopy with a laser source of ultrasound and piezoelectric detection of nanosecond ultrasonic pulses is used. Composite samples based on a silumin matrix with added silicon carbide (SiC) microparticles in different mass concentrations (3.8–15.5%) were investigated. As the concentration of SiC particles in a sample increases, its porosity that is determined using the hydrostatic-weighing method also increases. The simultaneous increase in the filler concentration and porosity leads to the appearance of a dispersion of the phase velocity of longitudinal acoustic waves in the sample within the frequency range of 3–25 MHz. The obtained empirical relationship between the relative change in the phase velocity and the sample porosity can be used to obtain a proximate quantitative estimate of the bulk porosity of the isotropic metal-matrix composite materials.

Acoustic Investigations of the Strained State of Hydrogenated 09G2S Steel

We study the acoustic properties of inhomogeneous plastically deformed specimens made of 09G2S steel. The specimens with residual strains were successively subjected to heat treatment and hydrogenation from the gas phase. After each procedure, we measured the space distributions of the velocity of longitudinal acoustic waves. We also analyzed the mechanisms of changes in the velocity in the course of hydrogenation in the region of the specimen with residual strains.

Combined effects of reinforcement fraction and porosity on ultrasonic velocity in SiC particulate aluminum alloy matrix composites

Abstract This work aims at applying the broadband laser-ultrasonic spectroscopy for quantitative evaluation of combined influence of the reinforcement fraction and the porosity content on the phase velocity of longitudinal acoustic waves in stir cast SiC particulate aluminum alloy matrix composites. The investigated composites contain 3.8–15.5 wt % of SiC particles with an average size of 14 μm. The growth of SiC fraction is accompanied by the growth of the total porosity content that reaches 4.7% for the maximum fraction of SiC. These combined factors cause the occurrence of dispersion of the phase velocity – it decreases in the frequency band 3–10 MHz and increases in the frequency band 20–40 MHz in comparison with that in the matrix without any reinforcement. It was found that the relative velocity dispersion increases with the growth of the porosity content within the investigated composite area regardless of the SiC fraction. The derived empirical relation between the relative velocity dispersion and the porosity content can be used for rapid quantitative porosity characterization in stir cast SiC particulate aluminum alloy matrix composites to reveal any potential areas with a reduced strength before the fabrication of composite products.